Completions frequently combine sections of screens that are connected directly or with short sections of blank pipe. The process of gravel packing is well known in the industry and comprises of depositing “gravel” typically a specialized sand in the annular space surrounding the screen assembly. The gravel is pumped through surface tubing into a tool known as a crossover and into the annular space that surrounds the screens. The gravel stays in the annular space but the carrier fluid goes through the screens and into an internal annulus between the screen and another pipe known as a wash pipe and back up into the wash pipe and out of the borehole through the crossover to an upper annulus above the production packer. One of the purposes of the gravel pack is to protect the screens from the erosive effects of high velocity gases by presenting a line of defense that diffuses the flow to protect the screen. The gravel also retains some of the solids carried with the production before those solids hit the screen to prolong screen useful life or to increase throughput during the life of the screen.
The nature of stacks of screens is that that the stack has dead zones where there are no screen openings. The delivered gravel tends to keep moving past these dead zones as the carrier fluid keeps moving until it finds screen openings to flow through and into the wash pipe. In horizontal completions this does not present a major issue as the gravel stays put due to the force of gravity so unpacked zones opposite connecting pipe does not risk exposing of screen in the event of a gravel pack shift. In wells that are closer to vertical than horizontal this can be a situation that allows some of the gravel pack to shift or settle by gravity away from the initial placement location to the annular space about the blank pipe separating the screen sections. This settling or shifting can leave portions of the screen assembly exposed to undesirable high velocity fluid, normally gas that can erode holes in the screens rendering such screens inoperative for their intended purpose.
For high deviation wells (close to horizontal), gravel packing may be used using low density proppant that have the propensity to float and be easily dragged by fluid flow. Gravel movement away from the screen could lead to screen exposure, formation sand production through the bare screen and potential screen erosion.
In the past efforts to avoid gravel pack voids have tried putting screened openings in the blank pipe connecting screen sections in an effort to encourage deposition of gravel outside the blank portions, mainly to enhance distribution of flow toward the screen sections.
A references discussing gravel packs and issues encountered in them is U.S. Pat. No. 7,934,555. External sleeves that swell to form isolators for expanded pipe in a borehole are discussed in general in U.S. Pat. No. 7,320,367.
The present invention addresses the gravel voids in boreholes by providing sleeves in those areas that have their smallest dimension when running in and when gravel is deposited and then swell in the presence of well fluids to take up the voids in the gravel pack around the connectors. In this way collapse of the existing gravel pack or low density proppant movement away from the screens is prevented while an effective gravel pack around the screens is assured. These and other aspects of the present invention will be more readily apparent to those skilled in the art from a review of the description of the preferred embodiment and the associated drawings while recognizing that the full scope of the invention is to be determined from the appended claims.